Investments in Unconsolidated Ventures (Narrative) (Details) usdPerAcre in Thousands, $ in Thousands	1 Months Ended					3 Months Ended			9 Months Ended		12 Months Ended
	Oct. 31, 2023	Oct. 31, 2022 USD ($)	Jul. 31, 2022 USD ($) a customHomeSite	Mar. 31, 2022 USD ($) hospitality	Oct. 31, 2021 USD ($) a	Sep. 30, 2023 USD ($) a	Sep. 30, 2022 USD ($)	Dec. 31, 2021 USD ($) a	Sep. 30, 2023 USD ($) a	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 a	Dec. 31, 2015 USD ($) ft² usdPerAcre	Mar. 30, 2022 USD ($)
Schedule of Investments [Line Items]
Total liabilities						$ 6,338,917			$ 6,338,917		$ 5,997,351
Equity in earnings (losses) from unconsolidated ventures						(30,886)	$ 7,708		(41,874)	$ 19,528
Jean-Georges Restaurants
Schedule of Investments [Line Items]
Acquisition interest				25.00%
Investments in unconsolidated ventures						30,800
Purchase price				$ 45,000
Number of hospitality | hospitality				40
Purchase price				$ 10,000
Additional interests acquired				20.00%
JDM Partners
Schedule of Investments [Line Items]
Acquisition interest								50.00%				50.00%
Floreo Development Holding Company, LLC
Schedule of Investments [Line Items]
Acquisition interest					50.00%
Purchase price					$ 59,000			$ 59,000
Equity Method Investments
Schedule of Investments [Line Items]
Equity Method Investments						211,801			211,801		232,392
Equity in earnings (losses) from unconsolidated ventures						(30,886)	7,708		(44,907)	14,890
Fulton Market Building
Schedule of Investments [Line Items]
Area of real estate property (in sqft) | a								20,000				20,000
Phoenix, Arizona | Floreo Development Holding Company, LLC
Schedule of Investments [Line Items]
Area of land | a					3,029
Floreo Development Holding Company, LLC
Schedule of Investments [Line Items]
Face amount		$ 165,000
Outstanding borrowings						65,400			65,400
Guarantee fee		$ 5,000
Floreo Development Holding Company, LLC | Equity Method Investments
Schedule of Investments [Line Items]
Investment in real estate and other affiliates						$ 56,500			$ 56,500
Floreo Development Holding Company, LLC | Phoenix, Arizona
Schedule of Investments [Line Items]
Area of land | a								3,029				3,029
West End Alexandria | Landmark Land Holdings
Schedule of Investments [Line Items]
Area of land | a								52				52
West End Alexandria | Alexandria
Schedule of Investments [Line Items]
Area of land | a								11				11
Foulger Pratt Development, LLC | Landmark Mall Property
Schedule of Investments [Line Items]
Area of land | a								33				33
Fair value of property contributed								$ 56,000
Fair value of property contributed, additional								$ 10,000
Seritage | Landmark Mall Property
Schedule of Investments [Line Items]
Area of land | a								19				19
Fair value of property contributed								$ 30,000
Over-Allotment Option
Schedule of Investments [Line Items]
Sale of stock, consideration received on transaction				$ 168,900
Disposal Group, Disposed of by Sale, Not Discontinued Operations | 110 North Wacker
Schedule of Investments [Line Items]
Consideration received				208,600										$ 208,600
Gain (loss) on disposal				5,000
Seaport Segment
Schedule of Investments [Line Items]
Area of real estate property (in sqft) | a						472,000			472,000
Seaport Segment | Tin Building by Jean-Georges
Schedule of Investments [Line Items]
Area of real estate property (in sqft) | ft²													53,783
Development Plans | Central Plaza
Schedule of Investments [Line Items]
Area of real estate property (in sqft) | a								4,000,000				4,000,000
Area of land | a								41				41
The Lawn Club NYC, LLC
Schedule of Investments [Line Items]
Joint venture real estate, percentage funded												80.00%
The Lawn Club NYC, LLC | Subsequent Event
Schedule of Investments [Line Items]
Joint venture real estate, percentage funded	90.00%
The Lawn Club NYC, LLC | Endorphin Ventures
Schedule of Investments [Line Items]
Joint venture real estate, percentage funded												20.00%
The Lawn Club NYC, LLC | Endorphin Ventures | Subsequent Event
Schedule of Investments [Line Items]
Joint venture real estate, percentage funded	10.00%
Ssäm Bar | Seaport Segment | Equity Method Investments
Schedule of Investments [Line Items]
Investment in real estate and other affiliates						$ 5,000			$ 5,000
Equity Method Investments						0			0		5,551
Equity in earnings (losses) from unconsolidated ventures						(5,478)	(216)		$ (5,981)	(473)
Tin Building by Jean-Georges
Schedule of Investments [Line Items]
Joint venture real estate, percentage funded									100.00%
Ownership interest									100.00%
Joint venture real estate, leased									100.00%
Tin Building by Jean-Georges | Seaport Segment | Equity Method Investments
Schedule of Investments [Line Items]
Equity Method Investments						12,800			$ 12,800		6,935
Contributions made by the company									36,600		$ 43,100
Investments in unconsolidated ventures						1,200
Equity in earnings (losses) from unconsolidated ventures						(9,879)	$ (11,366)		(30,736)	$ (20,565)
The Summit | Equity Method Investments
Schedule of Investments [Line Items]
Contribution of property													$ 13,400
SID bonds transferred to joint venture													1,300
Transaction value of land contributed to joint venture													$ 125,400
Transactional value per acre of land contributed to joint venture | usdPerAcre													226
Maximum contribution required to joint venture by co-venturer													$ 30,000
Amount contributed on maximum contribution required to joint venture by co-venture													$ 3,800
Area of land | a			54
Fair value of property contributed			$ 21,500
Equity in earnings (losses) from unconsolidated ventures			$ 13,500
Number of custom home sites | customHomeSite			28
Local Developer | Over-Allotment Option
Schedule of Investments [Line Items]
Sale of stock, consideration received on transaction				$ 22,100
Unconsolidated Properties
Schedule of Investments [Line Items]
Total liabilities						259,900			259,900
Unconsolidated Properties | Equity Method Investment, Nonconsolidated Investee or Group of Investees | HHC
Schedule of Investments [Line Items]
Total liabilities						$ 128,600			$ 128,600